China is modifying its domestically made strategic transport aircraft Y-20 to take on new missions like aerial refuelling, a military insider said.

A tanker variant for the Y-20 is now under development, the expert who is familiar with the matter, told the Global Times on Sunday on the condition of anonymity.

There were a series of reports over the past week, which claimed to have found a prototype for an aerial refuelling version of the Y-20 in a commercial satellite photo in Yanliang Airport in Xi'an, capital of Northwest China's Shaanxi Province.

China is in urgent need of an aerial refuelling tanker that has a larger fuel capacity than the HU-6, a tanker developed from the H-6 bomber, for its air force to become a strategic one, said the expert, noting that aerial refuelling enables a fighter jet to fly much farther without landing and reach more distant targets.

The J-20, China's most advanced stealth fighter jet, is able to receive aerial refuelling, China Central Television (CCTV) reported earlier this month.

Although China also operates a few Russian II-78 tankers, which are much larger than the HU-6, Russia was reluctant to sell more at a reasonable price, leading China to decide to develop its own large tanker, the expert said.

China's Y-20, a domestically made 200 ton-class large multi-purpose transport aircraft, is of similar size to the Russian Il-76 transport aircraft, on which the Il-78 is based, he said.

The aircraft began services in the People's Liberation Army Air Force in 2016, the Xinhua News Agency reported.

The fact that the Y-20 is domestically built means that Chinese developers can make alterations relatively easy and makes it a platform to develop more variants, the expert said.

China is experienced in making variants from transport aircraft in the past, reports said.

China modified the Y-9 transport aircraft into an early warning plane, patrol aircraft and anti-submarine aircraft, according to a CCTV report on Saturday.

The expert noted that it is also possible that China could make more Y-20 variants, noting that an early warning aircraft might be the most feasible one given the Y-20's size and endurance.